Submitted on March 9, 2009
Revised on March 26, 2009
Accepted on March 31, 2009
Endothelial-specific tetrahydrobiopterin expression accelerates refractory wound healing by suppressing oxidative stress in diabetes
Lu Tie1, Xue-Jun Li2, Xian Wang2, Keith M Channon3, and Alex F. Chen1*
1 University of Pittsburgh
2 Beijing Medical University
3 University of Oxford
* To whom correspondence should be addressed. E-mail: chena5{at}upmc.edu.
Refractory wound is a severe complication that leads to limb amputation in diabetes. Endothelial nitric oxide synthase (eNOS) plays a key role in normal wound repair, but is uncoupled in streptozotocin (STZ)-induced type 1 diabetes due to reduced cofactor tetrahydrobiopterin (BH4). We tested the hypothesis that overexpression of GTP cyclohydrolase I (GTPCH I), the rate-limiting enzyme for de novo BH4 synthesis, retards NOS uncoupling and accelerates wound healing in STZ mice. Blood glucose levels were significantly increased in both male endothelial-specific GTPCH I transgenic mice (Tg-GCH via a tie-2 promoter) and the wild-type (WT) littermates 5 days after STZ regimen. A full-thickness excisional wound was created on mouse dorsal skin by a 4-mm punch biopsy. Wound closure was delayed in STZ mice, which was rescued in STZ Tg-GCH mice. Cutaneous BH4 level was significantly reduced in STZ mice vs. WT mice, which was maintained in STZ Tg-GCH mice. In STZ mice, constitutive nitric oxide synthase (cNOS) activity and nitrite levels were decreased compared to WT mice, paralleled by increased superoxide anion (O2-) level and inducible nitric oxide synthase (iNOS) activity. In STZ Tg-GCH mice, nitrite level and cNOS activity were potentiated, O2- level and iNOS activity were suppressed compared to STZ mice. Thus, endothelial-specific BH4 overexpression accelerates wound healing in type 1 diabetic mice by suppressing oxidative stress.
